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Microbiology and Immunology, Loyola Univ. Chicago, Maywood, IL.

Introduction: Clean catch, anon-invasive urine collection method, is routinely used by physiciansfor urine cultivation and urinalysis. Since its development over 50years ago, the clean catch method has remained relatively unchanged,whereas more sensitive assays for detecting urinary bacteria havebeen developed. In light of these more sensitive assays (e.g. 16SrRNA gene sequencing and enhanced quantitative urine culture [EQUC]),an optimized method of urine collection should be determined. Here,we will focus on 3 separate aspects of the traditional clean catchmethod, including type of urine to collect (initial or midstream),time of urine collection, and the use of antiseptic wipes prior tocollection.
Objective: To optimize the method of cleancatch urine collection.
Rationale and Hypotheses: The sheerforce of urination through the urethra can dislodge urethral bacteriaand external genital bacteria. Initial stream urine is hypothesizedto contain a higher amount of urethral and genital bacteria becauseit is the first urine to flow passed and collect dislodged bacteria.It is hypothesized that by collecting midstream urine most of thedislodged bacteria will already be expelled and the urine willcontain less urethral and genital contamination.
Bacteria canreproduce exponentially in as little as 20 minutes. Cultures withlonger incubation times are expected to have higher colony formingunits (CFUs) than cultures with shorter incubation times. If we applythis concept to the bladder, we can hypothesize that first voids ofthe day, which have been “incubated” in the bladder overnight,should have higher bacterial abundance than urine samples collectedonly after a few hours of incubation, such as those collected in theafternoon or evening.
Antiseptic wipes used during traditionalclean catch are saturated in castile soap and hydrogen peroxide andare used to cleanse the genital area prior to urine collection. Theidea behind using antiseptic wipes is that they will eliminate anyexternal genital bacteria prior to collection, thereby reducinggenital contamination of voided urine specimens. However, castilesoap is only composed of natural plant-based oils and has limitedbactericidal capabilities. Castile soap, along with other types ofsoap, can create charged molecules that can capture and attach tonon-water soluble molecules including bacteria. With the addition ofwater, charged molecules that have already attached to bacteriabecome free-floating and can be rinsed away, carrying the bacteriawith them. Ironically, no water is used during the wiping process soit is possible that these wipes merely spread and relocate bacteriato other areas of the genitalia. Furthermore, it is possible thatduring urine collection the urine will act as water does and sweepthese free-floating charged molecules into the urine stream moreeasily, thereby causing an increase in genitalcontamination.
Methods: With IRB approval, periurethralswabs and voided urine specimens were collected daily from one youngadult female. Over the course of several months, conditions thatalter microbial composition of urine, such as the type of void, timeof void and use of antiseptic wipes prior to void, were assessed. Thepresence of microbes was detected using a modified expandedquantitative urine culture (MEQUC) followed by 16S rRNAsequencing.
Results: Periurethral swabs, on average, hadthe highest bacterial abundance, followed by initial stream urine andmidstream urine. There were insignificant changes in bacterialabundance based on time of collection. Following the use ofantiseptic wipes, changes in bacterial abundance and composition inboth the periurethral swabs and the midstream urines wereobserved.
Conclusions: Midstream urine contains the leastamount of genital contamination compared to initial stream and thetime of collection did not seem to impact either bacterial abundanceor diversity of midstream voided urines in one female. However, theuse of antiseptic wipes appeared to alter the bacterial compositionof both periurethral swabs and midstream urine, creating a midstreamurine sample that more resembled the periurethral swabs. We couldcome to this conclusion because the bacterial communities of thevoided urine and the periurethral swabs of this young woman differedsubstantially. This study is important for the development of futurestudies designed to compare the genitourinary microbiota ofindividuals in the community, as it provides us with a protocol thatgenerates reproducible data with voided urines and periurethralswabs, and alerts us to collection procedures that should be avoidedprior to sample collection.
References: na